Charge and frequency resolved isochronous mass spectrometry in storage rings: First direct mass measurement of the short-lived neutron-deficient $^{51}$Co nuclide

Abstract

Revolution frequency measurements of individual ions in storage rings require sophisticated timing detectors. One of common approaches for such detectors is the detection of secondary electrons released from a thin foil due to penetration of the stored ions. A new method based on the analysis of intensities of secondary electrons was developed which enables determination of the charge of each ion simultaneously with the measurement of its revolution frequency. Although the mass-over-charge ratios of 51 Co 27+ and 34 Ar 18+ ions are almost identical, and therefore, the ions can not be resolved in a storage ring, by applying the new method the mass excess of the short-lived 51 Co is determined for the first time to be ME( 51 Co) = −27342(48) keV. Shell-model calculations in the f p-shell nuclei compared to the new data indicate the need to include isospin-nonconserving forces.

Nuclear mass measurements with radioactive ion beams

“…A newer facility located at the Heavy Ion Research Facility in Lanzhou (HIRFL), [123][124][125][126][127][128] the cooler-storage-ring (HIRFL-CSRe) has begun operation in the last decade with mass measurements of over 60 nuclei and 20 first time measurements. [129][130][131][132][133][134][135][136] Both proton-rich and neutron-rich nuclei were re-measured or measured for the first time. Of these, a significant number of proton-rich pf -shell nuclei were measured for the first time at the CSRe with mass uncertainties δm/m ∼10 −7 -10 −6 .…”